JP2005516141A - Gas turbine configured to operate at a high exhaust gas recirculation rate and its operation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To relate to a gas turbine configured to operate in a high lean mode.
The gas turbine includes a compressor (3) configured to compress an oxidant (5) and means for receiving the compressed oxidant (7) and discharging combustion exhaust (9). The combustion chamber (3) configured as described above, the turbine (4), and the combustion exhaust (9) exiting from the combustion chamber (3) are recirculated and the combustion exhaust exits from the compressor (2). Combustion exhaust gas recirculation means (12, 13) configured to realize a high lean combustion mode at a combustion exhaust gas recirculation rate of 100% to 200% by mixing with the compressed oxidant (7). Have.

Description

  The present invention relates to a gas turbine and a method for operating the gas turbine.

Gas turbines operate on the basis of fossil fuel combustion. Today, two key requirements apply to the combustion process of fossil fuels in contrast to each other. For one thing, the combustion process achieves the maximum possible efficiency (to conserve fuel and reduce CO ₂ emissions), and on the other hand, the process is able to reduce pollutants (eg, NO _x ) Emissions are required to be minimized.

One of the most common ways to improve the efficiency of the combustion process is to use preheating the combustion air to a high temperature. This approach generates combustion at a relatively high flame temperature, while using a recuperative or regenerative heat exchanger to provide the combustion air with hot combustion exhaust energy. One drawback of the air temperature preheated to high temperature, flame, is exposed to elevated peak temperatures, in the formation process of the thermal NO _X, it is to bring about disastrous results.

  Research has been conducted on the combustion of hydrocarbons using lean reaction mixtures maintained at temperatures above the self-ignition threshold by recirculation of the combustion exhaust. By using this combustion exhaust gas, it becomes possible to dilute the reaction mixture and add energy to cause self-ignition.

Recirculation of the combustion exhaust increases the content of noble gases in the mixture. An early study of flammability limits for hydrocarbon and air combustion (Zabetakis, 1965) shows that flammable mixtures can be obtained for recirculation rates up to 50%. Recent studies aimed at providing reliable operating conditions for real systems have shown that recirculation rates of up to 30% can be used as NO _x reduction techniques [Wilkes ( Wilkes) and Gerhold, 1980]. The recirculation rate R is defined as the ratio of the flow rate of the recirculated combustion exhaust gas introduced into the combustion chamber and the flow rate of the fresh air-fuel mixture.

in this case,
G _IR = combustion exhaust gas recirculated in the combustion chamber G _ER = combustion exhaust gas recirculated outside the combustion chamber F = fuel O _x = fresh oxidant (usually air).

Recently, it has been found that flames can be stabilized at much higher flue gas recirculation rates. This can create a combustion mode that produces an invisible and inaudible flame. Such flames are associated with a uniform temperature and concentration distribution and no hot spots.

For the purposes of this specification, this alternative combustion mode, referred to as “highly diluted combustion”, occurs as a result of a very high level of dilution of the reaction mixture. The dilution of high level, to prevent the formation of temperature peaks localized, therefore, reduce the occurrence of NO _X. In order to realize an operation configuration that causes self-ignition of a flammable lean air-fuel mixture, it is necessary to achieve a gas mixture temperature that exceeds the self-ignition threshold. Such conditions result in a very low temperature difference between the initial flame temperature and the adiabatic flame temperature as compared to conventional undiluted visible flames.

in this case,
T _ad = adiabatic flame temperature (K)
T _in = initial temperature of reaction mixture (K)
ΔH _R = heat of reaction (kJ / kg)
c _p = specific heat of reaction mixture Y _Fuel = mole fraction of burned fuel R = recirculation rate F = molecular ratio of fuel O _x = molecular ratio of oxidant.

The above two equations show that the difference between the adiabatic flame temperature (T _ad ) and the initial temperature (T _in ) of the mixture decreases as R increases. Since the recirculation rate R is a result of the energy balance between the recirculated combustion exhaust and the fresh oxidant stream entering the combustion chamber, this affects the value of the initial temperature (T _in ). To do. However, the value of R does not affect the value of the adiabatic flame temperature (T _ad ), as shown by further modification of the above equation in connection with the standard equation for adiabatic combustion.

  in this case,

T _oxi = oxidant inlet temperature φ = equivalence ratio Y _oxi = oxidant mole fraction.

In the past, high lean combustion has been relied upon to inject fuel and air separately into the combustion chamber to obtain a two-stage mixing process. Before it can be ignited, fresh air is mixed with the recirculated combustion exhaust and further mixed with fuel to achieve the desired temperature conditions of the mixture. Patent document 1 reveals that a stable, highly lean and pollution-free flame can be obtained only for combustion exhaust gas recirculation rates higher than 200%. Furthermore, in practice, high lean combustion is only applied to high temperature processes operating at atmospheric pressure, such as processes used in the steel industry and processes related to glass manufacturing.

  This equivalence ratio parameter (φ) is often found in the standard literature of combustion and is simply defined as follows:

  The relative ratio λ of air and fuel is defined as follows.

in this case,
% Fuel and% air are the mole percentage (or mole fraction) of fuel and air, respectively, and are derived as follows:

And in this case
F _Air and F _Fuel are the molar flow rates of air and fuel, respectively.

The excess air amount is defined as e (%) = (λ−1) * 100.

Combustion is usually characterized by the stoichiometry of the reaction mixture.

λ <1 (φ> 1): Fuel rich mixture-rich stoichiometric air-fuel ratio λ = φ = 1: Theoretical air-fuel ratio condition λ> 1 (φ <1): Fuel lean state—lean stoichiometric air-fuel ratio

Gas turbines typically operate in a very lean flame (λ ≧ 2) at a flame temperature of about 1750 K at a pressure of about 20 bar with an oxidant (usually air) pressurized and preheated to 720 K. doing. A typical system has an ignition delay time of about 3 ms to 5 ms for a dwell time of about 20 ms. Target emission levels are less than 10 ppm for UHC and CO, and NO _x is single digit ppm (normalized with 15% O ₂ ). The conditions listed in these examples relate to gas turbines operating in the engine full load mode of operation and the above constraints need to be taken into account.

  The high lean combustion mode is achieved by recirculating a sufficient amount of combustion exhaust to the fresh mixture so that the resulting mixing temperature exceeds the autoignition threshold.

  Conventional techniques for high lean combustion (e.g., U.S. Pat. No. 6,057,097) are for high temperature processes (e.g., in a furnace) that are performed at atmospheric pressure (i.e., 1 bar). In this case, normal combustion takes place at 1 <λ <1.5 (in particular, λ = 1.1, ie 10% excess air). It has been shown that a recirculation rate higher than 200% is required to achieve a high lean combustion mode of invisible flame. Moreover, the prior art cites oxidant preheating as a requirement for high lean combustion.

  By realizing the high lean combustion mode in the gas turbine, it is possible to maintain the flame temperature at a desired operating value while further reducing the difference (ΔT) between the adiabatic temperature and the initial temperature. This helps to solve the problem of suppressing the high temperature point and provides advantages in terms of emission level and combustion efficiency by realizing a uniform temperature range.

In order to achieve high lean combustion in a gas turbine, it is necessary to consider temporal characteristics associated with the gas turbine. Diluting the reaction mixture has the effect of slowing the reaction rate of the process and thus affects both the ignition delay time and the overall reaction time.
US Pat. No. 5,154,599

  The object of the present invention is to define the application of high lean combustion technology to gas turbines, taking into account the associated operating conditions and constraints.

  In accordance with a first aspect of the invention, a gas turbine configured to operate in a high lean mode is defined, the turbine receiving a compressor configured to compress an oxidant and the compressed oxidant. A combustion chamber configured to realize a means for discharging the combustion exhaust, a turbine, and the combustion exhaust coming out of the combustion chamber are recirculated, and the combustion exhaust is compressed out of the compressor. And a combustion exhaust gas recirculation means configured to realize a high lean combustion mode at a combustion exhaust gas recirculation rate of 100% to 200%.

  Such gas turbines are configured to operate in a high lean combustion mode without the need to further preheat the oxidant before it is introduced into the combustion chamber. This is because the oxidizing agent is heated by the compression operation in the compressor. This is a requirement for a separate means for preheating the oxidant to achieve the autoignition of the diluted combustion / oxidant mixture that is necessary to achieve the specific combustion conditions. In contrast to the application of high lean combustion in the prior art.

  Conventional gas turbine systems typically use a lean premixed flame that is aerodynamically stabilized by a vortex flow device. In contrast, the gas turbine according to the first aspect of the present invention does not require such aerodynamic stabilization.

  In a particularly preferred embodiment, the flue gas recirculation means is configured to achieve a flue gas recirculation rate of 100% to 150%.

  In a preferred embodiment, the combustion exhaust gas recirculation means is configured to achieve combustion exhaust gas recirculation within the combustion chamber. In another preferred embodiment, the combustion exhaust gas recirculation means is configured to achieve combustion exhaust gas recirculation outside the combustion chamber. The combustion exhaust gas recirculation means is configured to recirculate the combustion exhaust gas coming out of the turbine. Preferably, the gas turbine is configured to cool the recirculated combustion exhaust coming out of the turbine and to supply the recirculated combustion exhaust coming out of the turbine along with the oxidant to the compressor. In a particularly preferred embodiment, the flue gas recirculation means is configured to combine the means inside and outside the combustion chamber to achieve flue gas recirculation.

  In a preferred embodiment, the gas turbine further comprises an oxidant preheating means configured to heat the compressed oxidant prior to charging the oxidant into the combustion chamber. Preferably, the oxidant preheating means comprises a heat exchanger configured to utilize the heat of the exhaust coming out of the turbine to heat the compressed oxidant. In a particularly preferred embodiment, the heat exchanger consists of a recuperator or regenerator. Preferably, the recirculated combustion exhaust leaving the turbine is cooled using this heat exchanger.

  In a preferred embodiment, the combustion exhaust recirculation means is configured to mix the premixed flow with the recirculated combustion exhaust before the fuel and oxidant premixed flow enters the combustion chamber. The

  In a preferred embodiment, the oxidant preheating means has an external heat source. In a particularly preferred embodiment, this external heat source comprises a catalytic precombustor.

  In a preferred embodiment, the oxidant is oxygen.

  In accordance with the second aspect of the present invention, a flameless steam-injected gas turbine is defined, the turbine for further diluting a gas turbine according to the first aspect of the present invention and an oxidant / fuel mixture. And a steam generator configured to make steam using the energy of the combustion exhaust coming from the turbine and supply the steam to the combustion chamber.

  In this preferred embodiment, the flameless steam-injected gas turbine operates as a closed loop system and further includes a condenser configured to condense the steam and reinject the generated water into the steam generator. .

  In a preferred embodiment, the flameless steam-injected gas turbine operates as an open loop system, while the steam generator is continuously refilled with water.

  In a preferred embodiment, a portion of the steam produced by the steam generator is supplied to the turbine to increase the turbine output power.

  In accordance with the third aspect of the present invention, a method for operating a gas turbine is defined, the method using a compressor that compresses the oxidant and means for receiving the compressed oxidant and discharging the combustion exhaust. Using a combustion chamber with a gas turbine, using a turbine, and recirculating the combustion exhaust coming out of the combustion chamber to mix the combustion exhaust with the compressed oxidant coming out of the compressor. Using a combustion exhaust gas recirculation means that realizes a high lean combustion mode with a combustion exhaust gas recirculation rate of 100% to 200%.

  In a particularly preferred embodiment, the method further comprises using a flue gas recirculation means that achieves a flue gas recirculation rate of 100% to 150%.

  In a preferred embodiment, the method comprises using a flue gas recirculation means that provides flue gas recirculation within the combustion chamber. In another preferred embodiment, the method comprises using a flue gas recirculation means that provides flue gas recirculation outside the combustion chamber. This method comprises using combustion exhaust recirculation means for recirculating the exhaust exhaust coming from the turbine. Preferably, the method further comprises cooling the recirculated combustion exhaust coming out of the turbine before supplying the recirculated combustion exhaust coming out of the turbine with the oxidant to the compressor. In a particularly advantageous embodiment, the method further comprises using a combustion exhaust recirculation means that combines the means inside and outside the combustion chamber to achieve combustion exhaust recirculation.

  In a preferred embodiment, the method comprises using an oxidant preheating means that heats the oxidant prior to charging the compressed oxidant into the combustion chamber. Preferably, the method uses a heat exchanger that implements the oxidant preheating means and utilizes the heat of the exhaust coming out of the turbine to heat the compressed oxidant. Using a vessel. In a particularly advantageous embodiment, the method comprises realizing the heat exchanger in the form of a recuperator or regenerator. The method includes using this heat exchanger to cool the recirculated combustion exhaust coming out of the turbine.

  In a preferred embodiment, the method uses a combustion exhaust recirculation means that mixes the recirculated combustion exhaust with the premixed flow of fuel and oxidant before entering the combustion chamber. Have

  In a preferred embodiment, the method comprises using an external heat source to achieve this oxidant preheating means. In a particularly advantageous embodiment, the method comprises using a catalytic precombustor to realize this external heat source.

  In a preferred embodiment, the method comprises using oxygen as the oxidant.

  In accordance with the fourth aspect of the present invention, a method for operating a flameless steam-injected gas turbine is defined, the method comprising using a gas turbine according to the first aspect of the present invention and mixing oxidant and fuel. To further dilute the gas, use a steam generator that produces the steam using the energy of the combustion exhaust coming out of the turbine and supplies the steam to the combustion chamber.

  In a preferred embodiment, the method operates the flameless steam-injected gas turbine as a closed loop system and uses a condenser to condense the steam and re-enter the generated water into the steam generator. Have

  In a preferred embodiment, the method includes operating the flameless steam-injected gas turbine as an open loop system and continuously refilling the steam generator with water.

  In a preferred embodiment, the method comprises supplying a portion of the steam produced by the steam generator to the turbine to increase the turbine output power.

  Here, for better understanding of the present invention, several embodiments of a gas turbine based on the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic view of a gas turbine 1 according to a first embodiment of the present invention in which a compressor 2, a combustion chamber 3 and a turbine 4 are provided. The principle of operation of the gas turbine and the operational relationship between the compressor 2, the combustion chamber 3 and the turbine 4 are very well known to those skilled in the art and will not be described in detail here. The invention is not limited by the type of compressor 2, turbine 4 or combustion chamber 3 used. For example, the combustion chamber 3 has a cylindrical shape, an annular shape, or an annular cylindrical shape. The choice of the type of combustion chamber 3 is determined by spatial constraints, mixing capacity, discharge capacity and the desired power level. Further, the present invention is not limited by the type of fuel used, and any fuel suitable for a gas turbine can be used in this embodiment and another embodiment of the present invention.

  The compressor 2 draws in the oxidant 5, which in this embodiment is air, from the outside environment and compresses it to the required operating pressure. Alternatively, other oxidants can be used, in which case the compressor is supplied with oxidant gas from a suitable storage means. The required operating pressure is 20 bar and the oxidant is heated to 720K by the compression operation. However, different pressures are required to use different turbine structures or other oxidants.

  The compressed oxidant 6 exits the compressor 2 and a portion 8 of this compressed oxidant is sent upstream of the turbine 4 bypassing the combustion chamber 3 for use as a coolant. This compressed oxidant portion 8 is 10% to 25% of the total compressed oxidant 6 output from the compressor 2. Alternatively, all of the compressed oxidant 6 exiting from the compressor can be sent directly to the combustion chamber 3. In full load operation, the compressed oxidant 6 typically has a temperature of 725 K and a pressure of 20 bar.

The compressed oxidant portion 7 that is not used as a coolant is then mixed with the recirculating combustion exhaust 12, 13 before being sent to the combustion chamber 3. In the combustion chamber 3, the mixture of fuel and compressed oxidant is burned in a highly lean mode with associated invisible and inaudible flames. The exhaust in the combustion chamber is generally 1800K. NO _X level, generally less than 5 ppm, CO level is less than 10 ppm.

  Fresh oxidant 7 and fresh fuel are injected into the combustion chamber 3 in such a way that corresponding mixing occurs between the oxidant 7, the fuel and the combustion exhaust 12, 13. This embodiment uses a premixed injection system that mixes the oxidant 7 and the flue gas 12, 13 prior to contact with fresh fuel. Alternatively, fresh fuel can be mixed with the combustion exhaust 12, 13 before being brought into contact with the fresh oxidant 7. However, different mixed configurations can be used based on the specific structure and requirements of the operating system. In other embodiments, a two-stage premix combustor can be used, where a portion of the combustion exhaust 12,13 is premixed with fresh oxidant 7 and the rest is fresh. Thorough mixing of these two mixtures, premixed with fuel, takes place in the downstream second stage mixer.

  In yet another embodiment, fresh oxidant 7 and fresh fuel can be supplied by a diffusion injection system, the aerodynamics of which is combusted before the fresh oxidant 7 contacts the fuel. It can be configured such that mixing occurs in the combustion chamber 3 such that the oxidant 7 and the fuel come into contact with the exhaust gas 12 and 13 at the final stage. Alternatively, the diffusion injection system can be configured such that the fuel first contacts the combustion exhaust 12, 13 before contacting the oxidant 7.

  The optimal mixing method depends on the spatial constraints of the system, the allowed pressure drop and the minimum required residence time.

  The stoichiometric air / fuel ratio of the fuel / air mixture does not have to be extremely lean as required by conventional lean premixed gas turbine systems. The equivalence ratio (φ) can be adjusted to achieve a reaction mixture above the autoignition temperature, the combustion of which meets the required turbine inlet temperature, producing low emissions. In this regard, the equivalence ratio of the reaction mixture, along with the combustion exhaust gas recirculation rate, is adjusted to meet such requirements.

  In this embodiment, the combustion exhaust gas is recirculated by combining means in the combustion chamber 3 at the inside 12 and outside 13. Alternatively, the exhaust gas recirculation can be carried out entirely either inside or outside the combustion chamber 3.

  Once combustion occurs, the combustion exhaust 9 exits the combustion chamber 3 and merges with a portion of the compressed oxidant 8 that is used as the coolant flow. Next, the mixture 10 of the combustion exhaust 9 and the oxidant 8 used as a coolant flow flows into the turbine 4. This exhaust gas mixture 10 drives the turbine 4, after which these exhaust gases are discharged as exhaust gas 11.

  A high level of flue gas recirculation is necessary to create an invisible, highly lean flame. The recirculation rate can be varied depending on the embodiment and can be varied during operation to meet different engine load requirements in the same combustion system. The exact selection of the recirculation rate and the distribution between the means in the combustion chamber 3 inside and outside 13 is determined by the system's mixture autoignition threshold, the recirculation system used, the minimum residence time, the allowed pressure drop And factors such as mixing capacity. When the gas turbine is operated at a zero recirculation rate, a standard non-diluted flame type combustion is performed.

FIG. 10 shows a comparison of the experimental results for a high lean flame at 100% recirculation rate and a standard undiluted flame at 0 recirculation rate. This experiment was conducted using natural gas as fuel and an inlet temperature of 600 ° C. FIG. 10 shows that the amount of NO _x produced by the highly lean flame is less sensitive to the flame temperature than the reference flame. At 1800 K, the lean flame shows a 40% reduction in the amount of NO _x produced compared to the reference flame.

Figure 10 is particularly for the generation of thermal NO _X is strongly dependent on the temperature, the higher ignition temperatures occur of the NO _X becomes a problem, combustion with flue gas recirculation for a high level of the NO _X generation It is effective in reducing the above. Based on this fact, the combustion exhaust gas recirculation and high lean combustion, in which can be alleviated in the general dilute flame used, well-known thermal NO _X generation problems in the gas turbine. Experiments have shown that NO _x associated with highly lean flames is greatly reduced by using an inlet temperature higher than 600 ° C. It also has the effect of high lean combustion extending the operating temperature range with better NO _x production capacity than the reference flame.

  Optically observing flames operating in common gas turbine conditions (eg, lean flames with an equivalence ratio of less than 0.6) to identify the boundaries with respect to the onset of invisible flames associated with high lean combustion Can do. It can be seen that in general gas turbine conditions, the invisible mode is achieved with a recirculation rate of 100%. Such a recirculation rate is significantly lower than the 300% recirculation rate that was stated to be a requirement in the prior art.

  At high temperatures, the use of prior art combustion at atmospheric pressure is usually performed at 1 <λ <1.5 (more precisely, λ = 1.1, ie 10% excess air). In gas turbine systems, the operating conditions are very different, λ is typically greater than 2 and the pressure is typically 20 bar. Under such conditions, it has been experimentally observed that for λ of 2 or more, a flue gas recirculation rate higher than 100% is sufficient to achieve an invisible flame associated with high lean combustion. Yes.

FIG. 13 shows a graph of typical gas turbine engine operation versus load for operating pressure and stoichiometric air / fuel ratio (λ or lambda). Optical observations show that the lower the value of λ, the lower the combustion exhaust gas recirculation rate required to allow the beginning of the high lean combustion mode. The process temperature of the gas turbine is controlled primarily by the stoichiometric air-fuel ratio of the reaction mixture, dilute the stoichiometric air-fuel ratio is lower and adiabatic flame temperature, and thus result in the emission of low NO _X for this purpose.

In the prior art, it is clear that combustion exhaust gas recirculation limits the process temperature. In the oxidant preheating high level, in order to limit the emission of NO _X, in order to control the process temperature requires a higher flue gas recirculation.

  In the prior art, flue gas recirculation mainly controls the process temperature because the flue gas is cooled before it is recirculated and the system becomes non-adiabatic. However, the combustion chamber 3 of the gas turbine needs to operate under conditions as close as possible to adiabatic conditions in order to produce high cycle efficiency. As a result, the cooling of the combustion exhausts 12 and 13 before recirculation is minimized, so that the combustion exhausts 12 and 13 are recirculated at a very high temperature. Become. These quasi-insulating conditions are useful for realizing a high lean combustion mode in the combustion chamber 3 of the gas turbine with a recirculation rate lower than that which is said to be necessary in the prior art.

  The optimum recirculation rate varies depending on the structure of the individual gas turbine and the individual operating conditions. Chemical kinetic studies can calculate information about the temporal characteristics and emission capabilities of gas turbine systems operating in high lean combustion modes. FIG. 11 shows a graph in which the residence time required to achieve the total burn of the air-fuel mixture with respect to the operating pressure is calculated. FIG. 11 shows that combustion exhaust gas recirculation rates from 100% to 200% have a significant effect on minimum residence time and ignition delay. However, these studies show that flue gas recirculation rates greater than 200% do not have a noticeable further effect in this regard.

  In addition, for atmospheric systems, gas turbines must meet severe pressure drop constraints. As the pressure drop associated with the gas turbine combustion system decreases, the cycle efficiency increases.

  In the embodiment of FIG. 1, the combustion exhaust gas recirculation 12 in the combustion chamber 3 is realized using high-speed injection. As the injection speed or momentum increases, the proportion of exhaust gas that is recirculated increases. However, higher injection speeds are also associated with higher pressure drops.

  Aerodynamic studies have shown that for a typical gas turbine system, the maximum recirculation rate achievable with simple high-speed injection varies from 100% to 200%, taking into account pressure drop constraints. This is shown (see FIG. 12).

  As FIG. 12 shows, the recirculation rate can be improved using additional equipment such as eddy current components. However, even with such equipment, the pressure drop limit is still easily reached when below 200%, which is disclosed as a requirement for high lean combustion in prior art atmospheric systems. .

  In a typical gas turbine system, the maximum pressure drop allowed for the combustor module is 3% of the total operating pressure. By using a single free injection, it is possible to achieve a recirculation rate greater than 200% while keeping the combustor / injector module pressure drop below the 3% limit. However, gas turbines operating under very large air-to-fuel ratios (ie, very lean mixtures) and severe spatial constraints cannot use a combustor based on a single free injection. High speed injector designs are limited by the inherent spatial constraints and pressure drop limitations associated with gas turbines. Each injection interferes with an adjacent injection, degrading the nominal entrapment capability of each individual injection.

FIG. 14 has a combustor module with 18 nozzles with a diameter of 20 mm, P = 22 bar, T _in = 470 ° C., air per combustor = 5.5 kg / s, fuel to combustor = 0 FIG. 6 is a graph of pressure drop versus recirculation rate in a gas turbine operating under the condition of .17 kg / s.

  FIG. 14 shows that in systems operating under the above conditions, the pressure drop limit is exceeded for recirculation rates greater than about 150%.

  Based on the above two studies, in gas turbine systems (characterized by high pressure and very lean stoichiometric air-fuel ratio), it is preferable to perform high lean combustion at a recirculation rate greater than 100%. This achieves an invisible flame associated with highly lean combustion that has no associated superheat point and a uniform temperature and concentration distribution.

  Chemical studies have shown that there are significant advantages in terms of process time associated with recycle rates greater than 100%. The study shows that this beneficial effect does not increase significantly for recirculation rates greater than 200%. Based on this, high lean combustion in the gas turbine system is preferably performed at a recirculation rate of 100% to 200%. However, aerodynamic studies indicate that high recirculation rates are associated with undesirably large pressure drops. Therefore, it is preferable to operate the gas turbine in a high lean mode with a recirculation rate less than 200%, more preferably less than 150%.

  In another embodiment of the invention, the combustion exhaust gas recirculation rate is not sufficient to meet the targeted thermal condition of the reactant fuel / oxidant mixture. For example, the temperature of the combustion chamber 3 of the mixture can be lower than the autoignition threshold of the fuel / oxidant mixture. This situation corresponds to a partial load operation in which the oxidant 1 is compressed at a lower pressure than the full load operation, so that when it exits the compressor 2, the temperature is lower. In such situations, additional oxidant preheating means are used to overcome this problem.

  FIG. 2 shows a schematic diagram of a gas turbine according to an embodiment of the invention using a heat exchanger 14 for further heating the compressed oxidant 7. A part of the exhaust gas 11 coming out of the gas turbine 4 is sent to a heat exchanger 14 that uses the residual heat of the exhaust gas 11 coming out of the turbine 4 to heat the compressed oxidant 7. In this embodiment, the heat exchanger 14 is in the form of a recuperator. Alternatively, the heat exchanger 14 can be in the form of a regenerator.

  If the residual heat of the exhaust gas 11 emerging from the turbine is not sufficient to heat the compressed oxidant 7 to the required temperature, an external heat source 16 is utilized (FIG. 3).

  Alternatively, as illustrated in FIG. 4, the catalytic precombustor 17 can heat the compressed oxidant 7 to the required temperature required for self-ignition of the fuel / oxidant mixture. In this embodiment utilizing partial load operation, the compressed oxidant is typically at a pressure of 13 bar and a temperature of 650K.

  A portion of the compressed oxidant 7 used for combustion is mixed with fuel under very lean conditions and sent to the catalytic precombustor 17 for introduction into the combustion chamber 3 at higher temperatures. The catalytic pre-combustor 17 operates in very lean conditions that ensure that additional thermal energy is added to the flow by surface reaction at the catalyst surface alone while minimizing emissions levels. . Also, operating the catalytic pre-combustor 17 in a very lean form helps to ensure that the reaction mixture entering the catalyst will not deactivate or overheat the catalyst. .

  In the embodiment as illustrated in FIG. 4, the combustion exhaust 13 recirculated out of the combustion chamber 3 passes further upstream of the catalytic precombustor 17 in order to add further thermal energy and dilute. 18 and downstream path 19 are combined and recirculated. Instead, the combustion exhaust gas 13 that is recirculated outside the combustion chamber 3 is recirculated only to either the upstream 18 or the downstream 19 of the catalytic precombustor 17. Combustion exhaust may have the effect of harming the catalytic function. Therefore, it is desirable to limit the combustion exhaust 13 flowing to the catalytic precombustor 17 to the minimum amount necessary to control the surface reaction and to control the temperature of the catalytic process.

  The embodiment is such that instead of allowing all of the compressed oxidant 7 to pass through the catalytic precombustor 17, a portion of the compressed oxidant 7 bypasses the catalytic precombustor 17. Can be configured. This is necessary to ensure an optimal stoichiometric air / fuel ratio for the catalytic precombustor 17 or for heating and cooling purposes. Similarly, it is desirable to inject a part of the fuel into the catalytic precombustor 17 and the rest directly into the combustion chamber 3.

  The catalytic pre-combustor 17 is configured to operate under very lean conditions (λ> 2.5) or very dense conditions (λ <0.5), depending on the optimal operating mode of the catalyst. be able to. The choice of operating mode depends on the individual ratios in each of the combustion exhaust 13, the compressed oxidant 7 and the fuel that enter or bypass the catalytic precombustor 17.

Typical conditions within the combustion chamber 3 of the embodiment shown in FIG. 4 include a temperature of 1650K. The NO _x level is generally less than 3 ppm and the CO level is less than 2 ppm.

  In another embodiment, the catalytic precombustor 17 is combined with additional heating means to further facilitate the preheating operation for the compressed oxidant 7. FIG. 5 schematically depicts an embodiment of the present invention that utilizes an external heat source 16 located upstream of the catalytic precombustor 17 to further heat the compressed oxidant 7.

  In yet another embodiment, this additional heating means is a heat exchanger 14 in the form of a recuperator, as depicted in FIG. Alternatively, the heat exchanger 14 can be in the form of a regenerator. In either case, the heat exchanger 14 utilizes the residual heat of the exhaust gas exiting the turbine 4 to heat the compressed oxidant before entering the catalytic precombustor 17. Yes.

  For this reason, all of the embodiments described thus far are based on the combustion exhaust 12 that is recirculated in the combustion chamber 3, the combustion exhaust 13 that is recirculated immediately after leaving the combustion chamber 3, or a combination of the two. It also uses combustion exhaust gas recirculation. In an alternative embodiment, the combustion exhaust 15 can be recirculated from the outlet of the turbine 4 as schematically illustrated in FIG.

  The embodiment of FIG. 7 can be used when high combustion exhaust gas recirculation cannot be completely achieved within the combustion chamber 3 and combustion exhaust gas recirculation outside the combustion chamber 3 causes too much pressure loss. . Combustion exhaust 15 is sent from the outlet of the turbine 4 and recycled to the inlet of the compressor 2 where it is mixed with fresh oxidant 5. Embodiments utilizing combustion exhaust gas recirculation in this manner may be applied in combination with combustion exhaust gas recirculation 12 within the combustion chamber 3 and / or high pressure combustion exhaust gas recirculation 13 outside the combustion chamber 3. it can. The amount of recirculation in proportion in the possible paths depends on several constraints such as pressure drop and thermal conditions and requirements to obtain a reaction mixture in the combustion chamber 3 that exceeds the autoignition threshold To do.

  The combustion exhaust 15 recirculated from the outlet of the turbine 4 is preferred from the standpoint of engine efficiency and must be cooled before mixing with the fresh oxidant stream 5. In the embodiment shown in FIG. 7, the extracted heat is utilized to heat the compressed oxidant 7 before it enters the combustion chamber 3 by the heat exchanger 14. The combustion exhaust gas is further cooled by taking out the remaining heat energy by the auxiliary component 20. Alternatively, the residual heat of the combustion exhaust 15 recirculated from the outlet of the turbine 4 can be utilized for different purposes or cooled by alternative means.

  This configuration can be applied to all the previously described embodiments with different solutions for preheating the compressed oxidant stream 7 or different ways of using the residual heat of the combustion exhaust 15.

  In another embodiment of the present invention, a gas turbine configured to operate in a high lean combustion mode includes a steam generation process for configuring a steam-injected gas turbine, as schematically depicted in FIG. Combined. Injecting the steam further dilutes the already highly diluted combustion mixture as a result of the high level combustion exhaust recirculation 12,13. Such a system can be referred to as a “Flameless Steam Injected Gas Turbine” (FSIGT).

Steam is generated by a steam generator 21 that generates steam by using the energy of the exhaust gas 11 coming out of the gas turbine 4. The steam 22 is supplied to the combustion chamber 3 in order to further dilute the combustion mixture and to suppress the formation of NO _x along the N ₂ O kinetic pathway.

  As shown in FIG. 8, the steam 23 is also injected downstream of the combustion chamber 3 in order to contribute to driving of the turbine 4. This has the effect of increasing the overall output of the system. Instead of this, it is also possible to inject the entire steam 22 into the combustion chamber 3.

  The system illustrated in FIG. 8 operates in a closed loop, and the steam exhausted with the exhaust gas 11 downstream of the gas turbine is regenerated in the condenser 24. The resulting water 25 is then re-entered into the steam generation process. The remaining combustion exhaust 26 passes through the condenser 24 and is discharged. Alternatively, the system can operate in an open cycle and can continuously supply fresh and clean water to the steam generator 21 through the water channel 27.

The advantage gained by the FSIGT system is to increase the efficiency of the gas turbine. Compared to a gas turbine that is not a steam injection turbine, the energy requirements remain the same for a given oxidant flow through the FSIGT compressor 2. However, the mass flow rate through the turbine 4 increases and increases the output power of the FSIGT. This allows the FSIGT system according to the invention to meet extremely low NO _x requirements while maximizing efficiency.

  In another embodiment, oxygen rather than air can be utilized as the oxidant. Thereby, the system of zero discharge can be operated. Any of the above-described embodiments can be configured to use oxygen as the oxidant.

An example of such a system is depicted in FIG. Oxygen 5 is compressed by the compressor 2 and supplied to the combustion chamber 3, where high-level combustion exhaust gas recirculation is realized by means of the inside 12 and the outside 13 of the combustion chamber 3. Combustion exhaust gas recirculation has the effect of mitigating the explosion effect of the reaction mixture of oxygen and fuel. In the entire process, because there is no nitrogen, without generating NO _X at all, combustion occurs.

  In embodiments that use oxygen as the oxidant, the dilution of the combustion exhaust has the effect of controlling the flame temperature. The exhaust gas 11 generated in the combustion chamber 9 drives the turbine 4 and its energy is further utilized (by the steam generator 21) to generate steam. A part of the steam 22 is injected into the combustion chamber 3 to control the process temperature, while the other part 23 is used to improve the output power of the turbine 23.

  The steam is mixed with the combustion products and then regenerated in the condenser 24 downstream of the steam generator. The remaining combustion exhaust 25, which is mainly carbon dioxide, is then cooled by the cooling means 26, and partly recycled to the compressor 2 to help dilute the combustion exhaust necessary to control the combustion process. Circulated. Excess carbon dioxide 27 can be removed and stored for another use.

  Those skilled in the art will recognize many more variations or improvements with reference to the exemplary embodiments described above, which have been presented for illustrative purposes only. And not intended to limit the scope of the invention, which is determined by the appended claims.

The schematic diagram of the gas turbine based on 1st embodiment of this invention Schematic diagram of a gas turbine based on the second embodiment of the present invention Schematic diagram of a gas turbine based on the third embodiment of the present invention Schematic diagram of a gas turbine based on the fourth embodiment of the present invention Schematic diagram of a gas turbine based on the fifth embodiment of the present invention Schematic diagram of a gas turbine based on the sixth embodiment of the present invention Schematic diagram of a gas turbine based on the seventh embodiment of the present invention Schematic diagram of a steam injection gas turbine based on the eighth embodiment of the present invention Schematic diagram of a steam injection gas turbine based on the ninth embodiment of the present invention Graph of NO _x level versus temperature for both a high lean flame at 100% recirculation rate and an undiluted flame at zero recirculation rate A graph of the minimum residence time of the mixture versus operating pressure for different recirculation rates Graph of recirculation rate against load Graph of both operating pressure versus load and theoretical air / fuel ratio (λ or lambda) for a typical gas turbine engine Graph of pressure drop against recirculation rate

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Gas turbine 2 Compressor 3 Combustion chamber 4 Turbine 5 Fresh oxidizer 6 Compressed oxidizer 7,8 A part of compressed oxidizer 9 Combustion exhaust 10 Mixture of oxidizer and combustion exhaust 11 Exhaust gas 12 Combustion chamber Exhaust gas recirculated 13 Combustion exhaust gas recirculated outside the combustion chamber 14 Heat exchanger 15 Combustion exhaust gas recirculated from the turbine outlet 16 External heat source 17 Catalytic pre-combustor 18 Upstream of the catalytic pre-combustor Path 19 Path downstream of catalytic pre-combustor 20 Auxiliary component 21 Steam generator 22, 23 Steam 24 Condenser 25 Combustion exhaust 26 Cooling means 27 Water channel, carbon dioxide

Claims (42)

A gas turbine configured to operate in a high lean mode,
A compressor configured to compress the oxidant;
A combustion chamber configured to receive the compressed oxidant and to discharge the combustion exhaust;
A turbine,
Recirculate the flue gas coming out of the combustion chamber and mix the flue gas with the compressed oxidant coming out of the compressor, with a flue gas recirculation rate of 100% to 200%, A gas turbine having combustion exhaust gas recirculation means configured to realize a high lean combustion mode.   The gas turbine according to claim 1, wherein the combustion exhaust gas recirculation means is configured to realize a combustion exhaust gas recirculation rate of 100% to 150%.   The gas turbine according to claim 1 or 2, wherein the combustion exhaust gas recirculation means is configured to realize combustion exhaust gas recirculation in the combustion chamber.   The gas turbine according to any one of claims 1 to 3, wherein the combustion exhaust gas recirculation means is configured to realize combustion exhaust gas recirculation outside the combustion chamber.   The gas turbine according to claim 4, wherein the combustion exhaust gas recirculation means is configured to recirculate the combustion exhaust gas coming out of the turbine.   6. The gas turbine according to claim 5, wherein the combustion exhaust gas that is recirculated from the turbine is cooled, and the recirculated combustion exhaust gas that is recirculated from the turbine is supplied to the compressor together with an oxidant. The gas turbine described.   The gas turbine according to any one of claims 1 to 6, wherein the combustion exhaust gas recirculation means is configured to realize combustion exhaust gas recirculation by combining means inside and outside the combustion chamber. .   A combustion exhaust gas recirculation means configured to mix recirculated combustion exhaust gas with the premixed flow of fuel and oxidant before entering the combustion chamber. The gas turbine as described in any one of to.   9. The gas turbine according to claim 1, further comprising oxidant preheating means configured to heat the oxidant before the compressed oxidant enters the combustion chamber.   10. A gas turbine according to claim 9, wherein the oxidant preheating means comprises a heat exchanger configured to utilize the heat of the exhaust coming from the turbine to heat the compressed oxidant.   The gas turbine according to claim 10, wherein the heat exchanger is configured as a recuperator or a regenerator.   The gas turbine according to claim 10 or 11, wherein the combustion exhaust gas recirculated out of the turbine is cooled using the heat exchanger.   The gas turbine according to any one of claims 10 to 13, wherein the oxidant preheating means has an external heat source.   The gas turbine according to claim 13, wherein the external heat source comprises a catalytic precombustor.   The gas turbine according to claim 1, wherein the oxidant is oxygen. A gas turbine according to any one of claims 1 to 15,
In order to further dilute the mixture of oxidant and fuel, the steam generator is configured to make steam using the energy of the combustion exhaust coming from the turbine and supply the steam to the combustion chamber. Non-flame steam injection gas turbine.   The non-flame steam-injected gas turbine operates as a closed-loop system and further comprises a condenser configured to condense the steam and re-enter the generated water into the steam generator. Flame steam injection gas turbine.   The flameless steam-injected gas turbine of claim 16, wherein the flameless steam-injected gas turbine operates as an open loop system and continuously supplies water to the steam generator.   19. A flameless steam-injected gas turbine according to any one of claims 16 to 18, wherein a portion of the steam produced by the steam generator is supplied to the turbine in order to increase the output power of the turbine. . Using a compressor to compress the oxidant;
Using a combustion chamber with means for receiving the compressed oxidant and discharging the combustion exhaust;
Using a turbine,
Recirculate the flue gas coming out of the combustion chamber and mix this flue gas with the compressed oxidant coming out of the compressor, with a flue gas recirculation rate of 100% to 200%, Using a combustion exhaust gas recirculation means to achieve a high lean combustion mode.   21. The method of claim 20, further comprising using a flue gas recirculation means that achieves a flue gas recirculation rate of 100% to 150%.   The method according to claim 20 or 21, comprising using a combustion exhaust gas recirculation means for realizing combustion exhaust gas recirculation in the combustion chamber.   23. A method according to any one of claims 20 to 22, comprising using a combustion exhaust gas recirculation means for realizing a combustion exhaust gas recirculation outside the combustion chamber.   24. The method of claim 23, further comprising using a combustion exhaust recirculation means for recirculating the combustion exhaust exiting the turbine.   25. The method of claim 24, further comprising cooling the combustion exhaust exiting the turbine prior to supplying the exhaust exhaust recirculated from the turbine to the compressor along with the oxidant.   26. A method as claimed in any one of claims 20 to 25, comprising using combustion exhaust gas recirculation means for combining the means inside and outside the combustion chamber to achieve combustion exhaust gas recirculation.   27. Use of a combustion exhaust recirculation means for mixing recirculated combustion exhaust with the premixed flow of fuel and oxidant prior to entering the combustion chamber. The method according to any one of the above.   28. A method as claimed in any one of claims 20 to 27, comprising using oxidant preheating means to heat the oxidant before it enters the combustion chamber.   In addition, the heat exchanger is used to realize the oxidant preheating means, and the heat exchanger is used to heat the compressed oxidant using the heat of the exhaust gas coming out of the turbine. 29. The method of claim 28, comprising:   30. The method of claim 29, further comprising realizing the heat exchanger in the form of a recuperator or regenerator.   31. A method according to claim 29 or 30 comprising using a heat exchanger in the case of claim 24 for cooling the combustion exhaust that is recirculated out of the turbine.   32. A method according to any one of claims 29 to 31, comprising using an external heat source to realize said oxidant preheating means.   33. The method of claim 32, further comprising using a catalytic precombustor to achieve the external heat source.   34. A method according to any one of claims 20 to 33, comprising using oxygen as the oxidant. Using the gas turbine according to any one of claims 1 to 15;
To further dilute the oxidant and fuel mixture using steam generated from the exhaust gas coming from the turbine and using a steam generator to supply the steam to the combustion chamber A method of operating a flameless steam injection gas turbine.   36. The method of claim 35, comprising operating the non-flame steam-injected gas turbine as a closed loop system, and using a condenser to condense the steam and re-enter the generated water into the steam generator. A method of operating a flame steam injection gas turbine.   37. The method of operating a flameless steam-injected gas turbine according to claim 36, comprising operating the flameless steam-injected gas turbine as an open loop system and continuously replenishing the steam generator with water.   36. A flameless flame as claimed in any one of claims 33 to 35, further comprising supplying a portion of the steam generated by the steam generator to the turbine to increase the output power of the turbine. A method of operating a steam-injected gas turbine.   A gas turbine substantially as described with reference to the drawings in the specification.   A flameless steam-injected gas turbine substantially as herein described with reference to the drawings.   A method of operating a gas turbine substantially as herein described with reference to the drawings.   A method of operating a flameless steam-injected gas turbine substantially as hereinbefore described with reference to the drawings.

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